Most Oneworld carriers have round-trip flights to various destinations in Europe at a discount today for $459-$608, NONSTOP or with a connection. Dates vary, use the linked calendar. Cheapest fares are mostly midweek. Most fares are not reversible.
Notes: The exact ranges for each destination will vary. Use the Google calendar view to get an idea of what dates work.
Some of these flights to smaller airports may require a long connection or two stops. When you begin your search, modify your filter to remove fares that have more than one connection, some smaller airports ONLY have flights with bad routing.
There is a good chance that other airlines will match these fares.
If you like this style of report, it’s a subset of daily Patreon recap [link]. That recap is the unfiltered list of every fare that was priced below the 6-month moving average.